1. Field of the Invention
The present invention relates to an arrangement of direct-bonding a plurality of integrated-circuit (IC) chips to a liquid crystal display (LCD) device so that the IC chips are electrically connected to the LCD device.
2. Description of the Related Art
FIG. 9 is a plan view of a conventional typical arrangement of bonding IC chips to an LCD device. A conventional LCD module 1 comprises an LCD device 2, three IC chips 3a, 3b and 3c bonded to the LCD device 2, and two flexible connector 4 and 5 in the form of a flexible printed wiring board. The LCD device 2 comprises an upper glass substrate 6 in the form of a rectangular board and a lower glass substrate 7 in the form of a rectangular board opposite to each other. However, the upper glass substrate 6 includes an end strip 6a extending beyond the end of the lower glass substrate 7. The lower surface of the end strip 6a has a scanning-lines driving IC chip 3c mounted thereto. The lower surface of the upper glass substrate 6 has transparent strip-shaped wiring patterns 8a formed thereon and connected to output electrodes of the IC chip 3c. The wiring patterns 8a extend along the longitudinal axis of the upper glass substrate 6 in parallel to one another except at connections between one end of the wiring patterns 8a and the output electrodes of the IC chip 3c. The lower surface of the end strip 6a has transparent wiring patterns 8b formed thereon and having one end connected to inputs of the IC chip 3c. The other end of the wiring patterns 8b is connected to electrically conductive patterns 5a formed on or in the flexible connector 5.
The lower glass substrate 7 includes a side edge strip 7a extending beyond a side edge (a lower edge in FIG. 9) of the upper glass substrate 6. The upper surface of the side edge strip 7a has two IC chips 3a and 3b mounted thereto for driving data lines. The upper surface of the lower glass substrate 7 has transparent strip-shaped wiring patterns 9a formed thereon and connected to output electrodes of the IC chips 3a and 3b. The wiring patterns 9a extend along the transverse axis of the lower glass substrate 7 in parallel to one another except at connections between one end of the wiring patterns 9a and the output electrodes of the IC chips 3a and 3b.
As shown in FIG. 9, the wiring patterns 8a on the upper glass substrate 6 and the wiring patterns 9a on the lower glass substrate 7 constitute a matrix-shaped wiring pattern shown in two-dot chain lines to provide a display area S. The upper surface of the side edge strip 7a has transparent wiring patterns 9b, 9c formed thereon and having one end connected to input electrodes of the IC chips 3a and 3b. The wiring patterns 9b and 9c are connected to strip-shaped electrically-conductive patterns 4b and 4c formed on the lower surface of the flexible connector 4. The upper surface of the flexible connector 4 includes linear wiring patterns 4a extending along the longitudinal axis of the flexible connector 4. One end (left-hand ends in FIG. 9) of the wiring patterns 4a is connected to the wiring patterns 4b via plated through-holes 4d formed in the flexible connector 4. The other end (right-hand ends in FIG. 9) of the wiring patterns 4a is connected to the wiring patterns 4c via plated through-holes 4d. Since the wiring patterns 4a cross the wiring patterns 4c, the wiring patterns 4a and 4c must be formed on the opposite sides of the flexible connector 4. In other words, the flexible connector 4 must be in the form of a double-sided flexible printed wiring board.
The conventional LCD module is expensive since as described above the wiring patterns 4a, 4b and 4c must be formed on the opposite sides of the flexible connector 4 and connected to each other via the through-holes 4d when the IC chips 3a and 3b are bonded to the side edge strip 7a of the LCD device 2. In addition, the flexible connector 4 is prolonged so that the wiring patterns 4b and 4c are connected to the wiring patterns 9b and 9c formed on the lower glass substrate 7. In principle, an amount of a change in length of an elongated object due to a temperature change is proportional to the length of the object. Therefore, the flexible connector 4 tends to experience a misalignment between the through-holes 4d and the wiring patterns 4a and 4c due to a heat in bonding and a defective electrical conduction due to a heat change with environmental change. Since the LCD module 1 has an arrangement of mounting the IC chip 3c to the lower surface of the upper glass substrate 6 and the IC chips 3b and 3c to the upper surface of the lower glass substrate 7, it requires the need for the two flexible connectors 4 and 5. In addition, since the direction of a thermocompression bonding of the IC chip 3c to the flexible connector 5 is opposite to the direction of a thermocompression bonding of the IC chips 3a and 3b to the flexible connector 4, a bonding step of an LCD module production is time-consuming.